A clever or unlucky man can make a bar of steel of many layers which is
less strong than a solid piece. Or about as strong. or stronger.
Unfortunately, the basis of laminated materials isn't so simple as
"Laminates are good because they ........."
MOst attention is devoted to laminated materials which are intentionally
strong.
Some laminated materials are chosen because the bond between the
laminated layers is weak, and this acts as a crack stopper... and
prevents brittle fracture of the whole, even though some of the
laminated layers are brittle.
Wood is a naturally occuring laminate. It is often an excellent choice
for understanding both the benefits and limitations of lamination.
Yes, there are limits or disadvantages to lamination, and usually those
are overcome by intelligent design.
Lamination allows plywood to be modestly stiff and modestly strong in
all directions within a board. A single board in the direction along the
grain will be both stiffer and stronger than the equivalent plywood.
The plywood will be neither highly stiff nor strong perpendicular to the
layers of woood. Some of the low properties can be sometimes attributed
to the adhesive which bonds these laminates (and the defects that can
develop in the bond lines).
In other words, lamination gives you something, but at a price... in
general.
So, when you search for the properties of lamination, remember that
there are plusses and minuses, as a generalization.
Large wooden beams are made by gluing together a lot of smaller wood
pieces, and these are laminates. In this case, one of the driving
motives is the lack of good lumber in those immense sizes, and
lamination is a good way to make the bulk required.
When one makes these large laminated wooden beams, one is able to select
the individual wooden laminates to be of high quality, and the resulting
quality of the entire massive beam would be higher than that of a
typical natural wooden single piece of that size. This is an example of
quality control possible in lamination which is not possible in large
monolithic blocks of materials.
Certainly, one can point out specific instances where the minuses are
quite minor.
Jim

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